Len Doyal, of the British Medical Association's ethics committee, writing in the June edition of the Royal Society of Medicine Journal Clinical Ethics, had said doctor-assisted deaths were already happening and needed to be regulated. He also said the law should be changed to enable doctors to give lethal injections even if patients cannot consent.

Dr Peter Saunders, campaign director of Care Not Killing, said: 'Doyal confuses euthanasia, in which the doctor actively ends the life of a patient under his care, with the appropriate withdrawal of treatment when its burden outweighs any benefit.

'The key issue ethically and legally is intention. Did the doctor intend to end the life of the patient or simply to ease their pain? Withdrawal of treatment is entirely appropriate when the burden that treatment imposes outweighs any benefit it brings. This is simply good medical practice. But to withdraw treatment with the intention of ending a patient's life, as opposed to relieving their symptoms, is unethical. It is possible to kill the pain without killing the patient. Claims by the pro-euthanasia lobby that seven out of ten patients die as a result of end of life decisions by doctors are grossly misleading. Terminally ill patients die as a result of their disease. Let's be clear about that.

'Doyal is however correct that if voluntary euthanasia were to be legalised on grounds of compassion involuntary euthanasia would be a logical consequence. We should take warning from this. Lord Joffe, in introducing his Assisted Dying for the Terminally Ill Bill, which was resoundingly defeated in the House of Lords last month, was very clear that he saw physician-assisted suicide as only a first step.

'Doyal is advocating the very worst form of medical paternalism whereby doctors could end the lives of patients after making a judgement that their lives are of no value and claim that they are simply acting in their patients' best interests. This is why the law should never be changed. Doctors should not be given that level of power.'

Saunders continued, 'The clear lesson from the Netherlands, where over 1,000 patients are killed by doctors every year without their consent and where babies with special needs are killed under the Groningen protocol, is that when voluntary euthanasia is legalised involuntary euthanasia inevitably follows.

'It is frightening that someone with such extreme views should be a co-opted member of the British Medical Association's Ethics Committee. Professor Doyal's presence is one of the reasons why the BMA adopted a neutral position on assisted dying last June despite strong reactions from grass-roots doctors.

'It is noteworthy that leading medical bodies including the Royal College of Physicians, the Royal College of General Practitioners, the Royal College of Nursing and the Association of Palliative Medicine are all strongly opposed to any change in the law which would legalise assisted dying. We are confident that the BMA will also see sense when it meets to reconsider its position later this month.'